LIMA, Ohio (AP) — President Donald Trump on Wednesday brought his re-election campaign to Ohio — a state essential to his 2020 strategy — touring a military tank plant and telling many of its cheering workers: "You better love me. I kept this place open."

Trump also used the visit to criticize John McCain, saying the late senator "didn't get the job done for our great vets." He complained that McCain's family didn't thank him for giving the senator "the kind of funeral that he wanted." McCain died last year of brain cancer.

Trump's visit to Ohio was his first since last year's midterm election campaign, when the state was a rare bright spot for Republicans in the upper Midwest. But with Trump's path to another four years in the White House relying on a victory here, his nascent campaign is mindful of warning signs that Ohio can hardly be taken for granted in 2020.

Perhaps no state has better illustrated the re-aligning effects of Trump's candidacy and presidency than Ohio, where traditionally Democratic-leaning working-class voters have swung heavily toward the GOP, and moderate Republicans in populous suburban counties have shifted away from Trump. It's for that reason, administration officials said, that Trump keeps returning to Ohio — this week's visit marks his 10th to the state since taking office.

The visit is part of a 2020 Trump strategy to appear in battleground states in his official White House capacity as much as possible this year, said a person with knowledge of the plans who was not authorized to speak publicly. Trump is expected to make similar trips throughout the year as he seeks to boost enthusiasm to counter an energized Democratic base. It's a strategy employed by previous presidents, both to leverage the prestige of office for political purposes and to offset the steep costs of presidential campaign travel with corresponding taxpayer-funded events.

Trump visited the Lima Army Tank Plant, which had been at risk for closure but is now benefiting from his administration's investments in defense spending. He also attended a re-election campaign fundraiser in Canton.

In this heavy manufacturing state, Trump cited his efforts to negotiate new trade agreements and enact tariffs to protect steel manufacturers. He described how his administration has confronted China over its trading practices and the "stealing" of American jobs and ideas.

For both parties, the results of the 2018 midterms have become a sort of "choose-your-own-adventure" moment for 2020 prognosticators. Republicans contend that the election of the state's GOP governor, Mike DeWine, largely mirrored Trump's 2016 path to victory and proves the strength of his coalition. They believe Trump's coattails in the state are long, as incumbent Republican congressional candidates in suburban counties — like Reps. Steve Chabot and Troy Balderson — won re-election last year in no small part because of the president's frequent visits.

"He's a fighter," said Ohio GOP Chair Jane Timken, "and that's one of the reasons why if you look at the Mahoning Valley, that's become a Republican portion of the state."

Democrats, for their part, highlight the re-election of Sen. Sherrod Brown, viewing his victory on a populist appeal as a signpost for their 2020 ticket. "A lot was driven by a realignment occurring among former Republican strongholds in the suburbs," said Ohio Democratic Party Chairman David Pepper. "With the right candidates, with the right message, 2020 could look a lot like Sherrod Brown's victory."

Nationally, Democrats have placed less of an emphasis on the traditional battleground state. Ohio was conspicuously absent from the list of key 2020 states — Wisconsin, Michigan, Pennsylvania and Florida — that are receiving a share of a $100 million investment by the Democratic super PAC Priorities USA. The state doesn't even make the PAC's "phase two" roster, which includes Nevada, Arizona, Georgia, North Carolina and New Hampshire.

The Republican National Committee, in laying the groundwork for the Trump campaign's field program, has maintained a constant presence in Ohio since 2012. Former RNC co-chair Bob Paduchik, who ran Trump's 2016 effort in the state, is repeating his role.

Trump visited days after he railed against the closure of a General Motors plant in Lordstown, a significant contributor to the economy in the eastern part of the state. The plant, which produced Chevy Cruze sedans, closed this month despite bipartisan pressure on the automaker, which claimed it was responding to consumer demand for larger vehicle types.

Trump said GM should re-open the plant or sell it to somebody who wants it. "Get it open now, don't wait," he said Wednesday.

Allies acknowledge he may be limited in what he can accomplish for the Lordstown plant, but said his vocal advocacy signaled to his supporters in the area that he is fighting on their behalf.

Trump continued his criticism of union leaders in his speech, saying, "They're not honest, and they ought to lower your dues, by the way." Last weekend he criticized a local union leader's handling of the GM plant closure.

Rep. Tim Ryan, D-Ohio, called Trump's attacks "disgraceful" and "beneath the office of the president of the United States."